1. Field of the Invention
The present invention relates to a filler applicable to degradable plastics considered to be available for the purpose of global environmental protection and a process for producing the same. More specifically, the filler is produced by using a filler, such as an extender pigment, e.g., calcium carbonate, and clay; an inorganic or organic pigment, e.g., titanium oxide, iron oxide, and phthalocyanine green, as a carrier material, adsorbing effective biodegradable and/or photodegradable component(s), such as starch, benzophenone, anthraquinone, transition metal salts, and oxidization accelerators, on the particle surface of the filler, as a uniform coating, via a surface treating agent, such as, a silane coupling agent, a fatty acid, a resin acid, or a salt thereof, after which the surface-treated filler is kneaded and filled in the plastics thereby uniformly dispersing the plastic-degradable effective component(s) in the plastics so as to be effectively put into practice.
2. Description of the Prior Art
Various environmental conditions on the earth are not permanent conditions imparted by humans, but are balanced in a closed ecological systems, "the earth", constructed and maintained as the result of life activities taking place over several billions of years since the beginning of life. For this reason, there never has been an inexhaustible capacity which admits all kinds of human activity which ignore the cartulary system. Consequently, essentially unlike naturally originating products such as wood and paper, having a cartulary cycle in the natural environment, artificial products, such as plastics, which are not part of the circulatory system in the environment, are impossible to assimilate into the environment after being diffused into the environment. Also, it is very difficult to carry out such activity as artificial treatments and recovery. These are the reasons why plastic degradation measures become a necessary proposition.
Recently, global environmental problems, such as atmospheric and ocean pollution, have been exposed. Measures for treating disposal products of plastics which are yearly produced in an amount of about one hundred million tons have been taken up globally. For these measures, filling up, burning up, recycling the disposal products, and other measures have been put into practice. However, these measures have not yet achieved essential settlement and, thus, for the moment, decrease in volume by the introduction of degradable plastics and apparent disappearance by their spontaneous purification have been attempted. In several countries, the examination has already been made to enforce rules and regulations, such as regulations for using non-degradable plastics and taxation of their use.
Plastics have excellent workabilities, and are suitable for mass production, are light, have high weather and chemical resistances, are easy to be colored, and have good decorative properties, in comparison with metals such as iron. Recently, plastics having improved in terms of physical/mechanical/thermal properties due to so-called engineering plastics have been developed. The total amount of plastic production in Japan has been increasing year by year and has now reached twelve million tons per year. Their application fields are very wide, i.e., they are used in industrial parts, automobiles, electrical household appliances, daily necessities, miscellaneous goods, and many other applications. Plastics are indispensable and useful for our lives as described above, but their non-degradability has been criticized not only as a source of environmental pollution but also as a major cause of global environmental problems. Accordingly, the development of degradable plastics have been strongly needed.
At present, degradable plastics have roughly been classified according to their degradation mechanism into biodegradable and photodegradable plastics. Furthermore, in the biodegradable plastics, degradable plastics in a narrow sense where polymers themselves are degraded by utilizing enzymes or microorganisms and biological breaking down plastics in which starch, etc. are incorporated in plastics and said starch, etc., are degraded to loose the forms of plastics themselves have been known. The term "photodegradable plastics" is intended to means plastics which are degraded by irradiating sun light, ultraviolet, etc. From the technical standpoint, those in which photodegradable groups, such as carbonyl, are introduced and those to which effective components, such as transition metal salts, oxidization accelerators, and photosensitizers, are added to impart photodegradabilities have been known. In any case, the most important problems are that these effective components are uniformly dispersed on the plastics.
In order to impart degradability to the plastics, in many cases, effective components are added in amounts ranging from 0.001 to 80 or 90 parts by weight based on the resin in spite of their degradation mechanism. Up to now, methods in which these components are kneaded separately from the fillers, such as a method involved in utilizing a master batch containing effective components, are applied as the addition method. However, conventional methods have poor operability, and are disadvantageous in that effective components can be uniformly mixed in products only with difficulty. Of these, since effective components cannot be uniformly mixed, these methods have serious problems that the effective components cannot be put into practice effectively, which leads to deteriorate quality such as deterioration in strength.